The invention refers to circulator pumps with two inlet ports and means to control these ports.
Instant hot water heaters are used alternatively to heat the domestic hot water and the heat carrier water of hydronic systems. For this purpose a three-way-valve is connected in series with the circulator pump whose first inlet port is connected with the domestic hot water circuit and whose second inlet port is connected with the hydronic circuit. When hot water is needed, the first inlet port is connected with the suction port of the impeller of the circulator pump; the change to room heating requires the closing of this first port and the opening of the second port, which needs two solenoid valves.
The invention shows a way to switch the suction port of a circulator pump from the first to the second circuit without any valves. This method is not restricted to circulator pumps for instant hot water heaters. According to the embodiments of the invention an electric circulator pump with spherical rotor is used.